Weather data recording started in Penallt in March 2011. The charts below show the monthly summaries from January 2015 until the end of December 2015 and also compare Penallt's 2015 weather with the 1971-2000 overall average data for Ross-on -Wye, the nearest place for which reliable data exist.
Monthly maximum and minimum temperatures
The chart shows that April was an unusually warm month, but July and (especially) August were disappointingly cool. The year ended with two warm months, with December being abnormally so, its mean maximum being 3.4°C above usual and the mean minimum being a dramatic 4.6°C above the Ross average.
- July 1st was the warmest day of the year with a maximum of 30.6°C
- February 2nd had the lowest maximum temperature of 2.7°C; there were no days with sub zero all day.
- Warmest by night was July 1st with a minimum of 16.7°C
- Coldest by night was January 19th, with a minimum temperature of -3.2°C
- There were 52 days on which the temperature exceeded 20°C and 21 when it was below 0°C, all but one of these being before May
- The mean annual temperature was 10.2°C, 0.5°C below the 2014 record warm year.
The mean annual temperature for England and Wales (1845 to 2012) is 9.3°C. The annual data for Penallt stretches back to 2012 (9.5°C) and 2013 (9.5°C), both years being about average overall. However, the 2014 figure is 0.9°C above the England/Wales average.
RainfallThe chart shows a very uneven distribution of rainfall throughout the year. Five months had in excess of 100 mm falling, with December's 236 mm being especially unwelcome. By contrast, April was a remarkably dry month.
Overall, the total rainfall for 2015 was 1178 mm (46.7 inches), 68% above the average Ross total of 706.2 mm (27.8 inches) showing that the year was much wetter than normal overall - not as wet as the 1508 mm of 2014 and the 1575 mm of 2012 however, but about the same as the 1158 mm of 2013.
- Rain was recorded on 216 days in the year
- The wettest day was May 3rd when 34.8 mm fell
- 20 mm or more fell on 14 different days